The present invention relates to a method of and apparatus for making plastic articles with embossed pattern.
A typical field of application of plastic articles with embossed pattern is the fabrication of injection-molded circuit boards, such as 3-D Molded Interconnected Devices (3-D MID) through hot stamping a pattern of conductor paths from a foil strip onto an injection-molded substrate. MIDs are formed parts with integrated conductive pathways and, compared to conventional circuit boards, afford enormous technical and rationalization potentials while substantially being more environmentally compatible. Through the provision of MIDs, electric and mechanical components can be integrated in circuit boards of almost any shape. MIDs enable completely different functions and contribute to a miniaturization of products. By saving mechanical components, the assembly is simplified while reliability in operation is enhanced.
Heretofore, plastic articles with a pattern that has been stamped under hot conditions have been made through several separate steps in a same way as the afore-mentioned 3-D MIDs. Reference is made, e.g., to German Pat. No. DE 197 32 353 A1. Plastic articles are initially made by using a conventional injection molding machine. Subsequently, the injection-molded plastic articles are subject to a stamping process in which the pattern is transferred from a foil strip onto the plastic articles under hot conditions. In order to realize a clean embossing operation, the plastic articles should be fat-free and dirt-free and pre-heated to a different temperature depending on the plastic material being used. In the event of intermediate storage, the plastic articles must therefore be preheated, cleaned and, possibly, degreased, before the embossing operation can be applied. Moreover, the plastic articles must be accurately positioned before placing the plastic foil strip in the stamping press. As currently the placement of the foil strip is done manually, an added error source must be accepted, when fabricating MIDs.
European Pat. No. EP 0 671 251 A1 describes an injection molding machine which has several processing stations, in particular when making multi-components injection-molded parts, whereby the actual injection steps and the other processing steps, such as cooling, ejecting, spraying and shaping of the injection-molded articles, are carried out in separate stations. By subdividing the overall production process in as many small units as possible, the cycle time should be shortened. This, however, significantly complicates the structure of the injection molding machine.
German Pat. No. 195 04 332 A1 describes the simultaneous fabrication and assembly of individual products through injection molding. The injection molding machine has cavities for molding plastic articles, wherein each injection-molding operation produces simultaneously in the respective cavities several different injection-molded articles which are then put together in the assembly spaces to a finished plastic product. A closing of the mold results in a closing of the cavities as well as of the assembly spaces, which remain closed during the injection process. During this time, the assembly spaces are inaccessible. This type of molding machine is not suitable for supply of foil strip material and transfer of patterns from the foil strip onto the injection-molded articles.
It would therefore be desirable and advantageous to provide an improved method and apparatus for making plastic articles that obviates prior art shortcomings and allows fabrication of plastic articles with an embossed pattern in a clean, rapid and precise manner, while still experiencing as little waste as possible.